Selection of multi-ring charged current $\nu_\mu$ 1$\pi^+$ samples and estimation of detector systematic uncertainties at T2K far detector

Abstract

Tokai to Kamioka (T2K) is an accelerator long baseline experiment that measures the neutrino oscillation parameters by observing $\nu_\mu$ ($\bar{\nu}_\mu$) disappearance and $\nu_e$ ($\bar{\nu}_e$) appearance from a $\nu_\mu$ ($\bar{\nu}_\mu$) beam. The experiment has both near and far detectors situated at 280 m and 295 km respectively from the beam production target. The far detector Super-Kamiokande where $\nu$ and $\bar{\nu}$ interact is a water Cherenkov detector. The dominant interactions at ∼0.6 GeV where T2K flux peaks are charged current quasi-elastic which result in single ring events. The next largest charged current interaction at T2K energy is resonant $1\pi$ production. The addition of charged current $\nu_\mu1\pi^+$ samples to the T2K analysis is expected to improve the precision on $\sin^{2}\theta_{23}$ and $|\Delta{m^2}_{32}|$. Studies on the selection of $\nu_\mu$ charged current $1\pi^+$ like events accumulated in forward horn current operation corresponding to a proton on target of $1.9663\times10^{21}$ are performed. The estimation of systematic uncertainty is important in the studies of sensitivity to neutrino oscillation parameters. One source of uncertainty is the impact of shortcomings in the detector model on the event selection. In our study, far detector systematic uncertainty is estimated via a fit to atmospheric neutrinos events collected in Super-Kamiokande, using a Markov Chain Monte Carlo Framework. We present the selection of $\nu_\mu$ charged current $1\pi^+$ multi-ring events and the process of estimation of detector systematic uncertainty.